Alleviator for hydraulic apparatus



. 1,640,046 ug- 7' 7 F McFARLAND AL EVIATORJ'OR HYDRAULIC APPARATUS"Filed Oct. 1a. 1926 Patented Aug. 23, 1927.

UNITED STATES PATENT OFFICE.

FRANK MCFARLAND, OF MEXICO, MISSOURI.

ALLEVIATOR FOR HYDRAULIC APPARATUS.

Application filed October 18, 1926. Serial No. 142,458.

main object to provide an alleviator of novel construction, which. is ofsuch design that it is impossible for the medium confined between theupper end of the plunger and the upper end of the cylinder of thealleviator to leak downward through the plunger and escape from thecylinder when the pump or other apparatus with which the alleviator isused is idle or not operating.

Figure 1 of the drawings isa top plan view of an hydraulic pump equippedwith an alleviator embodying my present invention; and v Figure 2 is anenlarged vertical sectional view of said alleviator.

In Figure 1 of the drawings A designates a conventional hydraulic pumpwhose discharge pipe 1 is provided with an alleviator of the generaltype disclosed in my United States patent previously referred to. Saidalleviator comprises a cylinder formed preferably from a base portion 2and a top portion 3 detachably connected together by fas tening devices4, and a plunger 5 reciprocatingly mounted in said cylinder. Thecylinder is provided at its lower end-with an opening 6 that establishescommunication between the interior of the cylinder and the dischargepipe 1 of the pump, and the plunger 5 is preferably hollow and providedat its lower end with a reduced extension 7 that constitutes a dash potelement which enters the opening 6 in the lower end of the cylinder asthe plunger 5.nears the end of its downward stroke. A medium is confinedbetween the upper end of the plunger and the top wall of the cylinder ofthe alleviator so as to exert downward pressure on the plunger inopposition to the upward pressure exerted on the plunger by the hquidbeing pumped, which medium will usually consist of oil at and air thatis trapped between the upper end of the cylinder and the surface of saidbody of oil.

In order to prevent said medium from leaking from the cylinder a packing8 is arranged between the exterior of the plunger 5 and the bottomportion 2 of the cylinder,

and a separate packing 9 arranged at the upper end of the bottom portionof the cylinder so as to surround the top portion 3 {17 of the cylinder.

As previously stated, the main object of 1y present invention is toprovide an alle- Viator which is of such construction that it impossiblefor the oil or air in the upper portion of the cylinder to leakdownwardly around the plunger 5 when the pump or other apparatus withwhich the alleviator is used is standing idle.

I To this end I provide the lower end of the cylinder with animperforate seat 10 that surrounds the'opening 6 therein, and pro videthe lower end of the plunger 5 with a gasket 11 that bears tightlyagainst said seat 10 when the plunger is at theend of its 5' downwardstroke, thereby effectively sealing the lower end of the cylinder of theallevia-tor. lVhen the plunger 5 moves downwardly' any liquid from the:discharge pipe of the pump that may be in the space between the seat 10on the end wall of the cylinder and the opposed lower end of the plunger5 is expelled from said space and forced back into the discharge pipethrough the joint between the reduced extension 7 on the plunger and theside wall of the hole 6 in the end wall of the cylinder which receivessaid extension, the extension 7 having a loose fit in the hole 6.

It is immaterial, so far as my broad idea is concerned, how theextension or dash pot element 7 is combined with the plunger 5, but inorder to simplify the construction and reduce the cost of manufacture ofthe alleviator, I prefer to form said extension from a member separateand distinct from the plunger and provide said member with a reducedexternally-screw-threaded portion 7 that is screwed into the lower endof the plunger 5. The gasket 11, previously referred to, is preferablyformed of fibre and is so proportioned that the inner portion of samewill be clamped between the end of the plunger 5 and the dash potelement 7 on the plunger, as such aconstruction insures the gasket 11being held securely in operative position on the plunger and permitssaid gasket to be replaced easily.

Having thus described my invention, whatI claim as new and desire tosecure by Letters Patent is:

1. In an alleviator of the kind that comprises a cylinder provided witha plunger that is acted upon by a medium confined between the upper endof the cylinder and the upper end of the plunger, an opening in thelower end of the cylinder, a reduced extension at the lower end of theplunger constructed so as to constitute adash pot element that enterssaid opening when the olun 'er' is at the end of its downward stroke,and means for producing a tight joint-between the lower end of thecylinder and thelower end of the plunger that surrounds the dashpotelement on the plunger.

2. In an alleviator of the kind that comprises a cylinder provided witha plunger that is acted upon by a medium confined between the upper endof the cylinder and the upper'end of the plunger, an opening in thelower end of the cylinder, a reduced extension at the lower end of theplunger constructed so as to constitute a dash pot element that enterssaid opening when the plunger is at the end of its downward stroke, afiat seat on thelower end wall of the cylinder which surrounds theopening in said wall, and a gasket at the lower end of the plungersurrounding the dash pot element thereon and adapted to press a ainstsaid seat when the plunger is at the end or" its downward stroke.

8. Inan'alleviator of the kind that comprises a cylinder provided with aplunger that is acted upon-by a medium confined between the upper end ofthe cylinder and the upper end of the plunger, an opening in the lowerend of the cylinder, a reduced extension at the lower end of the plungerconstructed so as to constitute a dash pot element that enters saidopening when the plunger is at the endof its downward stroke, a fiatseat on the lower end wall of the cylinder which surrounds the openingin said wall, and a gasket at the lower end of the plunger surroundingthe dash pot element thereon and adapted to press against'said seat whenthe plunger is at the end of its downward stroke, said dash pot elementhaving a loose fit in the opening in the end wall of the cylinder so asto provide for the escape of the liquid from the space between said endwall and the opposed end of the plunger when the plunger approaches theend of its downward stroke.

l. An'alleviator of the kind referred to, comprising a cylinder providedat its lower end with an opening that establishes communication betweenthe interior oi the cylinder and the apparatus'on which thealleviatoris'mo-unted, a reciprocating plunger in said cylinder whoseupward movement increases the pressure of a medium confined between theupper end'o'f the plunger and the top wall oi said cylinder, a dash potele mentat the lower-end of the plunger iormcd froma member providedwith a reduced portion that is screwed into the plunger, a flat seatsurrounding the opening in the lower end of the cylinder, and a gasketon the plunger confined in position by said dash pot element and adaptedto bear against the seat at the lower end of the cylinder.

FRANK MOFARLAND.

